Geneva: Syrian opposition leaders started leaving Geneva after air strikes on markets in the northwest killed at least 44 people, saying they could not take part in peace talks while civilians were dying daily.
In some of the deadliest violence since a ceasefire took effect in February, a suspected regime bombing raid yesterday hit a market in the city of Maaret al-Numan, killing at least 37 civilians, a monitor said.
Footage showed bloodied bodies scattered among twisted metal stalls in a street strewn with fruit and vegetables.
Another strike on a fish market in the nearby town of Kafranbel killed seven civilians, said the Syrian Observatory for Human Rights, a Britain-based monitoring group.
The strikes were in Idlib province, which is under the control of Al-Qaeda's Syrian offshoot Al-Nusra Front.
Like the Islamic State group, Al-Nusra is excluded from the ceasefire and regime forces have continued offensives in areas under its control.
The main opposition High Negotiations Committee condemned the strike on Maaret al-Numan as a "massacre" and clear violation of the truce.
"It is a dangerous escalation of an already fragile situation, showing contempt for the whole international community at a time when there is supposed to be a cessation of hostilities," said spokesman Salem al-Meslet.
The raid was "Assad's response" to the HNC's decision to suspend its formal participation in negotiations.
"Our decision to postpone our participation in the Geneva talks was taken to highlight the cynicism of the regime in pretending to negotiate while escalating the violence... The world must not ignore this challenge," said Meslet.
The troubled talks -- the latest in a long series of efforts to end Syria's five-year conflict -- failed to get off the ground this week despite hopes brought on by the ceasefire.
The partial truce, brokered by the United States and Russia, led to a dramatic drop in violence across Syria but a recent surge in fighting, especially around second city Aleppo, has raised fears of its total collapse.
The opposition announced Monday it was putting its participation on hold to protest escalating violence and restrictions on humanitarian access.
HNC coordinator Riyad Hijab said Tuesday that he and other delegates were beginning to leave Geneva.